/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.tomcat.util.http.fileupload;

import org.apache.tomcat.util.http.fileupload.FileUploadBase.FileUploadIOException;
import org.apache.tomcat.util.http.fileupload.util.Closeable;
import org.apache.tomcat.util.http.fileupload.util.Streams;

import java.io.ByteArrayOutputStream;
import java.io.*;

/**
 * <p> Low level API for processing file uploads.
 * <p>
 * <p> This class can be used to process data streams conforming to MIME
 * 'multipart' format as defined in
 * <a href="http://www.ietf.org/rfc/rfc1867.txt">RFC 1867</a>. Arbitrarily
 * large amounts of data in the stream can be processed under constant
 * memory usage.
 * <p>
 * <p> The format of the stream is defined in the following way:<br>
 * <p>
 * <code>
 * multipart-body := preamble 1*encapsulation close-delimiter epilogue<br>
 * encapsulation := delimiter body CRLF<br>
 * delimiter := "--" boundary CRLF<br>
 * close-delimiter := "--" boundary "--"<br>
 * preamble := &lt;ignore&gt;<br>
 * epilogue := &lt;ignore&gt;<br>
 * body := header-part CRLF body-part<br>
 * header-part := 1*header CRLF<br>
 * header := header-name ":" header-value<br>
 * header-name := &lt;printable ascii characters except ":"&gt;<br>
 * header-value := &lt;any ascii characters except CR &amp; LF&gt;<br>
 * body-data := &lt;arbitrary data&gt;<br>
 * </code>
 * <p>
 * <p>Note that body-data can contain another mulipart entity.  There
 * is limited support for single pass processing of such nested
 * streams.  The nested stream is <strong>required</strong> to have a
 * boundary token of the same length as the parent stream (see {@link
 * #setBoundary(byte[])}).
 * <p>
 * <p>Here is an example of usage of this class.<br>
 * <p>
 * <pre>
 *   try {
 *     MultipartStream multipartStream = new MultipartStream(input, boundary);
 *     boolean nextPart = multipartStream.skipPreamble();
 *     OutputStream output;
 *     while(nextPart) {
 *       String header = multipartStream.readHeaders();
 *       // process headers
 *       // create some output stream
 *       multipartStream.readBodyData(output);
 *       nextPart = multipartStream.readBoundary();
 *     }
 *   } catch(MultipartStream.MalformedStreamException e) {
 *     // the stream failed to follow required syntax
 *   } catch(IOException e) {
 *     // a read or write error occurred
 *   }
 * </pre>
 */
public class MultipartStream {

	/**
	 * The Carriage Return ASCII character value.
	 */
	public static final byte CR = 0x0D;

	// ----------------------------------------------------- Manifest constants
	/**
	 * The Line Feed ASCII character value.
	 */
	public static final byte LF = 0x0A;
	/**
	 * The dash (-) ASCII character value.
	 */
	public static final byte DASH = 0x2D;
	/**
	 * The maximum length of <code>header-part</code> that will be
	 * processed (10 kilobytes = 10240 bytes.).
	 */
	public static final int HEADER_PART_SIZE_MAX = 10240;
	/**
	 * The default length of the buffer used for processing a request.
	 */
	protected static final int DEFAULT_BUFSIZE = 4096;
	/**
	 * A byte sequence that marks the end of <code>header-part</code>
	 * (<code>CRLFCRLF</code>).
	 */
	protected static final byte[] HEADER_SEPARATOR = {CR, LF, CR, LF};
	/**
	 * A byte sequence that that follows a delimiter that will be
	 * followed by an encapsulation (<code>CRLF</code>).
	 */
	protected static final byte[] FIELD_SEPARATOR = {CR, LF};
	/**
	 * A byte sequence that that follows a delimiter of the last
	 * encapsulation in the stream (<code>--</code>).
	 */
	protected static final byte[] STREAM_TERMINATOR = {DASH, DASH};
	/**
	 * A byte sequence that precedes a boundary (<code>CRLF--</code>).
	 */
	protected static final byte[] BOUNDARY_PREFIX = {CR, LF, DASH, DASH};
	/**
	 * The input stream from which data is read.
	 */
	private final InputStream input;

	// ----------------------------------------------------------- Data members
	/**
	 * The amount of data, in bytes, that must be kept in the buffer in order
	 * to detect delimiters reliably.
	 */
	private final int keepRegion;
	/**
	 * The byte sequence that partitions the stream.
	 */
	private final byte[] boundary;
	/**
	 * The length of the buffer used for processing the request.
	 */
	private final int bufSize;
	/**
	 * The buffer used for processing the request.
	 */
	private final byte[] buffer;
	/**
	 * The progress notifier, if any, or null.
	 */
	private final ProgressNotifier notifier;
	/**
	 * The length of the boundary token plus the leading <code>CRLF--</code>.
	 */
	private int boundaryLength;
	/**
	 * The table for Knuth-Morris-Pratt search algorithm
	 */
	private int[] boundaryTable;
	/**
	 * The index of first valid character in the buffer.
	 * <br>
	 * 0 <= head < bufSize
	 */
	private int head;

	/**
	 * The index of last valid character in the buffer + 1.
	 * <br>
	 * 0 <= tail <= bufSize
	 */
	private int tail;

	/**
	 * The content encoding to use when reading headers.
	 */
	private String headerEncoding;

	/**
	 * <p> Constructs a <code>MultipartStream</code> with a custom size buffer.
	 * <p>
	 * <p> Note that the buffer must be at least big enough to contain the
	 * boundary string, plus 4 characters for CR/LF and double dash, plus at
	 * least one byte of data.  Too small a buffer size setting will degrade
	 * performance.
	 *
	 * @param input     The <code>InputStream</code> to serve as a data source.
	 * @param boundary  The token used for dividing the stream into
	 *                  <code>encapsulations</code>.
	 * @param bufSize   The size of the buffer to be used, in bytes.
	 * @param pNotifier The notifier, which is used for calling the
	 *                  progress listener, if any.
	 * @throws IllegalArgumentException If the buffer size is too small
	 * @since 1.3.1
	 */
	public MultipartStream(InputStream input,
	                       byte[] boundary,
	                       int bufSize,
	                       ProgressNotifier pNotifier) {

		if (boundary == null) {
			throw new IllegalArgumentException("boundary may not be null");
		}
		// We prepend CR/LF to the boundary to chop trailing CR/LF from
		// body-data tokens.
		this.boundaryLength = boundary.length + BOUNDARY_PREFIX.length;
		if (bufSize < this.boundaryLength + 1) {
			throw new IllegalArgumentException(
					"The buffer size specified for the MultipartStream is too small");
		}

		this.input = input;
		this.bufSize = Math.max(bufSize, boundaryLength * 2);
		this.buffer = new byte[this.bufSize];
		this.notifier = pNotifier;

		this.boundary = new byte[this.boundaryLength];
		this.boundaryTable = new int[this.boundaryLength + 1];
		this.keepRegion = this.boundary.length;

		System.arraycopy(BOUNDARY_PREFIX, 0, this.boundary, 0,
				BOUNDARY_PREFIX.length);
		System.arraycopy(boundary, 0, this.boundary, BOUNDARY_PREFIX.length,
				boundary.length);
		computeBoundaryTable();

		head = 0;
		tail = 0;
	}

	// ----------------------------------------------------------- Constructors

	/**
	 * <p> Constructs a <code>MultipartStream</code> with a default size buffer.
	 *
	 * @param input     The <code>InputStream</code> to serve as a data source.
	 * @param boundary  The token used for dividing the stream into
	 *                  <code>encapsulations</code>.
	 * @param pNotifier An object for calling the progress listener, if any.
	 * @see #MultipartStream(InputStream, byte[], int, ProgressNotifier)
	 */
	MultipartStream(InputStream input,
	                byte[] boundary,
	                ProgressNotifier pNotifier) {
		this(input, boundary, DEFAULT_BUFSIZE, pNotifier);
	}

	/**
	 * Compares <code>count</code> first bytes in the arrays
	 * <code>a</code> and <code>b</code>.
	 *
	 * @param a     The first array to compare.
	 * @param b     The second array to compare.
	 * @param count How many bytes should be compared.
	 * @return <code>true</code> if <code>count</code> first bytes in arrays
	 * <code>a</code> and <code>b</code> are equal.
	 */
	public static boolean arrayequals(byte[] a,
	                                  byte[] b,
	                                  int count) {
		for (int i = 0; i < count; i++) {
			if (a[i] != b[i]) {
				return false;
			}
		}
		return true;
	}

	// --------------------------------------------------------- Public methods

	/**
	 * Retrieves the character encoding used when reading the headers of an
	 * individual part. When not specified, or <code>null</code>, the platform
	 * default encoding is used.
	 *
	 * @return The encoding used to read part headers.
	 */
	public String getHeaderEncoding() {
		return headerEncoding;
	}

	/**
	 * Specifies the character encoding to be used when reading the headers of
	 * individual parts. When not specified, or <code>null</code>, the platform
	 * default encoding is used.
	 *
	 * @param encoding The encoding used to read part headers.
	 */
	public void setHeaderEncoding(String encoding) {
		headerEncoding = encoding;
	}

	/**
	 * Reads a byte from the <code>buffer</code>, and refills it as
	 * necessary.
	 *
	 * @return The next byte from the input stream.
	 * @throws IOException if there is no more data available.
	 */
	public byte readByte() throws IOException {
		// Buffer depleted ?
		if (head == tail) {
			head = 0;
			// Refill.
			tail = input.read(buffer, head, bufSize);
			if (tail == -1) {
				// No more data available.
				throw new IOException("No more data is available");
			}
			if (notifier != null) {
				notifier.noteBytesRead(tail);
			}
		}
		return buffer[head++];
	}

	/**
	 * Skips a <code>boundary</code> token, and checks whether more
	 * <code>encapsulations</code> are contained in the stream.
	 *
	 * @return <code>true</code> if there are more encapsulations in
	 * this stream; <code>false</code> otherwise.
	 * @throws FileUploadIOException    if the bytes read from the stream exceeded the size limits
	 * @throws MalformedStreamException if the stream ends unexpectedly or
	 *                                  fails to follow required syntax.
	 */
	public boolean readBoundary()
			throws FileUploadIOException, MalformedStreamException {
		byte[] marker = new byte[2];
		boolean nextChunk = false;

		head += boundaryLength;
		try {
			marker[0] = readByte();
			if (marker[0] == LF) {
				// Work around IE5 Mac bug with input type=image.
				// Because the boundary delimiter, not including the trailing
				// CRLF, must not appear within any file (RFC 2046, section
				// 5.1.1), we know the missing CR is due to a buggy browser
				// rather than a file containing something similar to a
				// boundary.
				return true;
			}

			marker[1] = readByte();
			if (arrayequals(marker, STREAM_TERMINATOR, 2)) {
				nextChunk = false;
			} else if (arrayequals(marker, FIELD_SEPARATOR, 2)) {
				nextChunk = true;
			} else {
				throw new MalformedStreamException(
						"Unexpected characters follow a boundary");
			}
		} catch (FileUploadIOException e) {
			// wraps a SizeException, re-throw as it will be unwrapped later
			throw e;
		} catch (IOException e) {
			throw new MalformedStreamException("Stream ended unexpectedly");
		}
		return nextChunk;
	}

	/**
	 * <p>Changes the boundary token used for partitioning the stream.
	 * <p>
	 * <p>This method allows single pass processing of nested multipart
	 * streams.
	 * <p>
	 * <p>The boundary token of the nested stream is <code>required</code>
	 * to be of the same length as the boundary token in parent stream.
	 * <p>
	 * <p>Restoring the parent stream boundary token after processing of a
	 * nested stream is left to the application.
	 *
	 * @param boundary The boundary to be used for parsing of the nested
	 *                 stream.
	 * @throws IllegalBoundaryException if the <code>boundary</code>
	 *                                  has a different length than the one
	 *                                  being currently parsed.
	 */
	public void setBoundary(byte[] boundary)
			throws IllegalBoundaryException {
		if (boundary.length != boundaryLength - BOUNDARY_PREFIX.length) {
			throw new IllegalBoundaryException(
					"The length of a boundary token cannot be changed");
		}
		System.arraycopy(boundary, 0, this.boundary, BOUNDARY_PREFIX.length,
				boundary.length);
		computeBoundaryTable();
	}

	/**
	 * Compute the table used for Knuth-Morris-Pratt search algorithm.
	 */
	private void computeBoundaryTable() {
		int position = 2;
		int candidate = 0;

		boundaryTable[0] = -1;
		boundaryTable[1] = 0;

		while (position <= boundaryLength) {
			if (boundary[position - 1] == boundary[candidate]) {
				boundaryTable[position] = candidate + 1;
				candidate++;
				position++;
			} else if (candidate > 0) {
				candidate = boundaryTable[candidate];
			} else {
				boundaryTable[position] = 0;
				position++;
			}
		}
	}

	/**
	 * <p>Reads the <code>header-part</code> of the current
	 * <code>encapsulation</code>.
	 * <p>
	 * <p>Headers are returned verbatim to the input stream, including the
	 * trailing <code>CRLF</code> marker. Parsing is left to the
	 * application.
	 * <p>
	 * <p><strong>TODO</strong> allow limiting maximum header size to
	 * protect against abuse.
	 *
	 * @return The <code>header-part</code> of the current encapsulation.
	 * @throws FileUploadIOException    if the bytes read from the stream exceeded the size limits.
	 * @throws MalformedStreamException if the stream ends unexpectedly.
	 */
	public String readHeaders() throws FileUploadIOException, MalformedStreamException {
		int i = 0;
		byte b;
		// to support multi-byte characters
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		int size = 0;
		while (i < HEADER_SEPARATOR.length) {
			try {
				b = readByte();
			} catch (FileUploadIOException e) {
				// wraps a SizeException, re-throw as it will be unwrapped later
				throw e;
			} catch (IOException e) {
				throw new MalformedStreamException("Stream ended unexpectedly");
			}
			if (++size > HEADER_PART_SIZE_MAX) {
				throw new MalformedStreamException(String.format(
						"Header section has more than %s bytes (maybe it is not properly terminated)",
						Integer.valueOf(HEADER_PART_SIZE_MAX)));
			}
			if (b == HEADER_SEPARATOR[i]) {
				i++;
			} else {
				i = 0;
			}
			baos.write(b);
		}

		String headers = null;
		if (headerEncoding != null) {
			try {
				headers = baos.toString(headerEncoding);
			} catch (UnsupportedEncodingException e) {
				// Fall back to platform default if specified encoding is not
				// supported.
				headers = baos.toString();
			}
		} else {
			headers = baos.toString();
		}

		return headers;
	}

	/**
	 * <p>Reads <code>body-data</code> from the current
	 * <code>encapsulation</code> and writes its contents into the
	 * output <code>Stream</code>.
	 * <p>
	 * <p>Arbitrary large amounts of data can be processed by this
	 * method using a constant size buffer. (see {@link
	 * #MultipartStream(InputStream, byte[], int,
	 * MultipartStream.ProgressNotifier) constructor}).
	 *
	 * @param output The <code>Stream</code> to write data into. May
	 *               be null, in which case this method is equivalent
	 *               to {@link #discardBodyData()}.
	 * @return the amount of data written.
	 * @throws MalformedStreamException if the stream ends unexpectedly.
	 * @throws IOException              if an i/o error occurs.
	 */
	public int readBodyData(OutputStream output)
			throws MalformedStreamException, IOException {
		return (int) Streams.copy(newInputStream(), output, false); // N.B. Streams.copy closes the input stream
	}

	/**
	 * Creates a new {@link ItemInputStream}.
	 *
	 * @return A new instance of {@link ItemInputStream}.
	 */
	ItemInputStream newInputStream() {
		return new ItemInputStream();
	}

	/**
	 * <p> Reads <code>body-data</code> from the current
	 * <code>encapsulation</code> and discards it.
	 * <p>
	 * <p>Use this method to skip encapsulations you don't need or don't
	 * understand.
	 *
	 * @return The amount of data discarded.
	 * @throws MalformedStreamException if the stream ends unexpectedly.
	 * @throws IOException              if an i/o error occurs.
	 */
	public int discardBodyData() throws MalformedStreamException, IOException {
		return readBodyData(null);
	}

	/**
	 * Finds the beginning of the first <code>encapsulation</code>.
	 *
	 * @return <code>true</code> if an <code>encapsulation</code> was found in
	 * the stream.
	 * @throws IOException if an i/o error occurs.
	 */
	public boolean skipPreamble() throws IOException {
		// First delimiter may be not preceeded with a CRLF.
		System.arraycopy(boundary, 2, boundary, 0, boundary.length - 2);
		boundaryLength = boundary.length - 2;
		computeBoundaryTable();
		try {
			// Discard all data up to the delimiter.
			discardBodyData();

			// Read boundary - if succeeded, the stream contains an
			// encapsulation.
			return readBoundary();
		} catch (MalformedStreamException e) {
			return false;
		} finally {
			// Restore delimiter.
			System.arraycopy(boundary, 0, boundary, 2, boundary.length - 2);
			boundaryLength = boundary.length;
			boundary[0] = CR;
			boundary[1] = LF;
			computeBoundaryTable();
		}
	}

	/**
	 * Searches for a byte of specified value in the <code>buffer</code>,
	 * starting at the specified <code>position</code>.
	 *
	 * @param value The value to find.
	 * @param pos   The starting position for searching.
	 * @return The position of byte found, counting from beginning of the
	 * <code>buffer</code>, or <code>-1</code> if not found.
	 */
	protected int findByte(byte value,
	                       int pos) {
		for (int i = pos; i < tail; i++) {
			if (buffer[i] == value) {
				return i;
			}
		}

		return -1;
	}

	/**
	 * Searches for the <code>boundary</code> in the <code>buffer</code>
	 * region delimited by <code>head</code> and <code>tail</code>.
	 *
	 * @return The position of the boundary found, counting from the
	 * beginning of the <code>buffer</code>, or <code>-1</code> if
	 * not found.
	 */
	protected int findSeparator() {

		int bufferPos = this.head;
		int tablePos = 0;

		while (bufferPos < this.tail) {
			while (tablePos >= 0 && buffer[bufferPos] != boundary[tablePos]) {
				tablePos = boundaryTable[tablePos];
			}
			bufferPos++;
			tablePos++;
			if (tablePos == boundaryLength) {
				return bufferPos - boundaryLength;
			}
		}
		return -1;
	}

	/**
	 * Internal class, which is used to invoke the
	 * {@link ProgressListener}.
	 */
	public static class ProgressNotifier {
		/**
		 * The listener to invoke.
		 */
		private final ProgressListener listener;

		/**
		 * Number of expected bytes, if known, or -1.
		 */
		private final long contentLength;

		/**
		 * Number of bytes, which have been read so far.
		 */
		private long bytesRead;

		/**
		 * Number of items, which have been read so far.
		 */
		private int items;

		/**
		 * Creates a new instance with the given listener
		 * and content length.
		 *
		 * @param pListener      The listener to invoke.
		 * @param pContentLength The expected content length.
		 */
		ProgressNotifier(ProgressListener pListener, long pContentLength) {
			listener = pListener;
			contentLength = pContentLength;
		}

		/**
		 * Called to indicate that bytes have been read.
		 *
		 * @param pBytes Number of bytes, which have been read.
		 */
		void noteBytesRead(int pBytes) {
	        /* Indicates, that the given number of bytes have been read from
             * the input stream.
             */
			bytesRead += pBytes;
			notifyListener();
		}

		/**
		 * Called to indicate, that a new file item has been detected.
		 */
		void noteItem() {
			++items;
			notifyListener();
		}

		/**
		 * Called for notifying the listener.
		 */
		private void notifyListener() {
			if (listener != null) {
				listener.update(bytesRead, contentLength, items);
			}
		}

	}

	/**
	 * Thrown to indicate that the input stream fails to follow the
	 * required syntax.
	 */
	public static class MalformedStreamException extends IOException {

		/**
		 * The UID to use when serializing this instance.
		 */
		private static final long serialVersionUID = 6466926458059796677L;

		/**
		 * Constructs a <code>MalformedStreamException</code> with no
		 * detail message.
		 */
		public MalformedStreamException() {
			super();
		}

		/**
		 * Constructs an <code>MalformedStreamException</code> with
		 * the specified detail message.
		 *
		 * @param message The detail message.
		 */
		public MalformedStreamException(String message) {
			super(message);
		}

	}

	/**
	 * Thrown upon attempt of setting an invalid boundary token.
	 */
	public static class IllegalBoundaryException extends IOException {

		/**
		 * The UID to use when serializing this instance.
		 */
		private static final long serialVersionUID = -161533165102632918L;

		/**
		 * Constructs an <code>IllegalBoundaryException</code> with no
		 * detail message.
		 */
		public IllegalBoundaryException() {
			super();
		}

		/**
		 * Constructs an <code>IllegalBoundaryException</code> with
		 * the specified detail message.
		 *
		 * @param message The detail message.
		 */
		public IllegalBoundaryException(String message) {
			super(message);
		}

	}

	/**
	 * An {@link InputStream} for reading an items contents.
	 */
	public class ItemInputStream extends InputStream implements Closeable {

		/**
		 * Offset when converting negative bytes to integers.
		 */
		private static final int BYTE_POSITIVE_OFFSET = 256;
		/**
		 * The number of bytes, which have been read so far.
		 */
		private long total;
		/**
		 * The number of bytes, which must be hold, because
		 * they might be a part of the boundary.
		 */
		private int pad;
		/**
		 * The current offset in the buffer.
		 */
		private int pos;
		/**
		 * Whether the stream is already closed.
		 */
		private boolean closed;

		/**
		 * Creates a new instance.
		 */
		ItemInputStream() {
			findSeparator();
		}

		/**
		 * Called for finding the separator.
		 */
		private void findSeparator() {
			pos = MultipartStream.this.findSeparator();
			if (pos == -1) {
				if (tail - head > keepRegion) {
					pad = keepRegion;
				} else {
					pad = tail - head;
				}
			}
		}

		/**
		 * Returns the number of bytes, which have been read
		 * by the stream.
		 *
		 * @return Number of bytes, which have been read so far.
		 */
		public long getBytesRead() {
			return total;
		}

		/**
		 * Returns the number of bytes, which are currently
		 * available, without blocking.
		 *
		 * @return Number of bytes in the buffer.
		 * @throws IOException An I/O error occurs.
		 */
		@Override
		public int available() throws IOException {
			if (pos == -1) {
				return tail - head - pad;
			}
			return pos - head;
		}

		/**
		 * Returns the next byte in the stream.
		 *
		 * @return The next byte in the stream, as a non-negative
		 * integer, or -1 for EOF.
		 * @throws IOException An I/O error occurred.
		 */
		@Override
		public int read() throws IOException {
			if (closed) {
				throw new FileItemStream.ItemSkippedException();
			}
			if (available() == 0 && makeAvailable() == 0) {
				return -1;
			}
			++total;
			int b = buffer[head++];
			if (b >= 0) {
				return b;
			}
			return b + BYTE_POSITIVE_OFFSET;
		}

		/**
		 * Reads bytes into the given buffer.
		 *
		 * @param b   The destination buffer, where to write to.
		 * @param off Offset of the first byte in the buffer.
		 * @param len Maximum number of bytes to read.
		 * @return Number of bytes, which have been actually read,
		 * or -1 for EOF.
		 * @throws IOException An I/O error occurred.
		 */
		@Override
		public int read(byte[] b, int off, int len) throws IOException {
			if (closed) {
				throw new FileItemStream.ItemSkippedException();
			}
			if (len == 0) {
				return 0;
			}
			int res = available();
			if (res == 0) {
				res = makeAvailable();
				if (res == 0) {
					return -1;
				}
			}
			res = Math.min(res, len);
			System.arraycopy(buffer, head, b, off, res);
			head += res;
			total += res;
			return res;
		}

		/**
		 * Closes the input stream.
		 *
		 * @throws IOException An I/O error occurred.
		 */
		@Override
		public void close() throws IOException {
			close(false);
		}

		/**
		 * Closes the input stream.
		 *
		 * @param pCloseUnderlying Whether to close the underlying stream
		 *                         (hard close)
		 * @throws IOException An I/O error occurred.
		 */
		public void close(boolean pCloseUnderlying) throws IOException {
			if (closed) {
				return;
			}
			if (pCloseUnderlying) {
				closed = true;
				input.close();
			} else {
				for (; ; ) {
					int av = available();
					if (av == 0) {
						av = makeAvailable();
						if (av == 0) {
							break;
						}
					}
					skip(av);
				}
			}
			closed = true;
		}

		/**
		 * Skips the given number of bytes.
		 *
		 * @param bytes Number of bytes to skip.
		 * @return The number of bytes, which have actually been
		 * skipped.
		 * @throws IOException An I/O error occurred.
		 */
		@Override
		public long skip(long bytes) throws IOException {
			if (closed) {
				throw new FileItemStream.ItemSkippedException();
			}
			int av = available();
			if (av == 0) {
				av = makeAvailable();
				if (av == 0) {
					return 0;
				}
			}
			long res = Math.min(av, bytes);
			head += res;
			return res;
		}

		/**
		 * Attempts to read more data.
		 *
		 * @return Number of available bytes
		 * @throws IOException An I/O error occurred.
		 */
		private int makeAvailable() throws IOException {
			if (pos != -1) {
				return 0;
			}

			// Move the data to the beginning of the buffer.
			total += tail - head - pad;
			System.arraycopy(buffer, tail - pad, buffer, 0, pad);

			// Refill buffer with new data.
			head = 0;
			tail = pad;

			for (; ; ) {
				int bytesRead = input.read(buffer, tail, bufSize - tail);
				if (bytesRead == -1) {
					// The last pad amount is left in the buffer.
					// Boundary can't be in there so signal an error
					// condition.
					final String msg = "Stream ended unexpectedly";
					throw new MalformedStreamException(msg);
				}
				if (notifier != null) {
					notifier.noteBytesRead(bytesRead);
				}
				tail += bytesRead;

				findSeparator();
				int av = available();

				if (av > 0 || pos != -1) {
					return av;
				}
			}
		}

		/**
		 * Returns, whether the stream is closed.
		 *
		 * @return True, if the stream is closed, otherwise false.
		 */
		@Override
		public boolean isClosed() {
			return closed;
		}

	}

}
